To still my beating mind.

Dr. Hans Selye, who earlier in this century pioneered the concept of stress, conducted an interesting experiment to demonstrate the remarkable anti-stress benefits of walking. In his experiment, done at the University of Montreal, where he was a professor, Dr. Selye subjected 10 rats to a month-long program of electric shock, blinding lights, and loud noises. At the end of the month all 10 animals were dead because of the negative impact the stress had on their health.

During the second phase of this experiment, Dr. Selye had 10 rats walk on treadmills until they were in good physical condition, and then subjected them to the same stress program as the first group. At the end of one month all 10 of the physically conditioned rats remained alive and reasonably well (if perhaps somewhat disoriented). Dr. Selye concluded that physical fitness buffered the rats against the health-destroying effects of stress.

I recently selected 36 physically inactive women, and randomly divided them into walking and sedentary control groups. The test group walked at a brisk pace 45 minutes per day, five days a week, for 15 weeks, while the control group remained inactive. The study was tightly supervised, with the walkers exercising under the direction of a research assistant, who carefully monitored intensity and duration of exercise.

Heart and lung fitness was measured three times during the study to document improvement in ability to exercise. We also measured psychological well-being three times during the study using the General Well-Being Scale (see p. 12).

The dramatic results of our study were recently published in the Journal of Psychosomatic Research. After just six weeks of exercise, the walkers improved their psychological well-being scores from an average of 70 (which indicates a stress problem) to 81 (indicating positive well-being), maintaining this throughout the 15-week study. The inactive control group did not experience any significant change in their score. Other psychological tests showed that the walkers, over time, had higher energy levels, felt more relaxed and less tense or anxious, and sensed that life was more satisfying and interesting.

Brain satisfaction. The part of the brain that enables us to exercise, the motor cortex, lies only a short distance away from the part of the brain strata that deals with thought and feeling. Might their proximity mean that when exercise stimulates the motor cortex, it has a parallel effect on cognition, emotion, and psychological mood state?

Since the beginning of time many have believed in the "cerebral satisfaction" of exercise. The Greeks maintained that exercise made their minds more lucid. Aristotle started his "peripatetic school" in 335 B.C. The school was so named because of his habit of walking up and down (peripaton) the paths of the Lyceum in Athens while thinking or lecturing to his students who walked with him.

Plato and Socrates had also practiced the art of peripatetics, as did later the Roman or do vagorum, or walking scholars. Centuries later Oliver Wendell Holmes explained that "in walking the will and the muscles are so accustomed to working together and perform their task with so little expenditure of force that the intellect is left comparatively free."

The highly acclaimed Perrier Survey of Fitness in America, conducted by Louis Harris and Associates, showed that men and women today strongly believe in the value of exercise for the mind. The survey found that those with a deep commitment to exercise reported feeling more relaxed, less tired, and more disciplined, a sense of looking better, greater self-confidence, greater productivity in work, and in general, more of being at one with themselves.

The 1988 Campbell's Survey on Well-Being in Canada revealed that physically active people have less depression and higher levels of positive well-being than inactive individuals. When active people are asked why they exercise, the most common response is "to feel better mentally and physically." A survey by Runner's World magazine discovered that although most people start running to "improve physical fitness," most continue to run to "improve mental fitness" and to "relieve stress."

Recently Dr. Tom Stephens of Canada studied data from four other national surveys in the U.S. and Canada. "The inescapable conclusion from these four national studies," says Dr. Stephens, "is that physical activity is positively associated with good mental health, especially positive mood, general well-being, and less anxiety and depression." This relationship was found to be stronger for the older age group (40 - - years of age) than for the younger, and for women more than for men.

While life events of all types (marriage, divorce, buying a house, losing a job, moving, surgery, etc.) are significant stressors, recent studies have shown that such stress has less negative impact on physically active individuals.

For example, in a four-year study of 278 managers from 12 different corporations, physical activity was found to have a buffering effect on the relationship between life events and illness. In other words, corporate managers who were active experienced less health problems from stress than inactive managers.

Many other studies have shown the value of physical activity for improved mental health. For instance, research at Duke University showed that after 10 weeks of walking and jogging 135 minutes a week, exercising adults experienced decreased anxiety, depression, and fatigue, with elevated vigor.

Dr. John Griest of the University of Wisconsin compared the effects of a running program against psychotherapy with depressed subjects. Running was found to be at least as effective as psychotherapy in alleviating moderate depression.

In a compelling study by Dr. James MacMahon of Stanford University, two hours per week of running and hard basketball led to significant improvements in self-concept and moods of delinquent adolescent males.

Why exercise makes you feel better. Positive feelings after exercise have been known to last not only for several hours but throughout the day as exercise becomes a habit.

Just why this happens is still unresolved. Some of the theories involve the effects of exercise on various hormones and other body chemicals.

The body has an amazing hormonal system of morphine-like chemicals called endogenous opioids. These are of interest because their receptors are found in the areas of the brain associated with emotion, pleasure, pain, and behavior. During exercise, the pituitary increases its productions of one of these chemicals, B-endorphin, helping you to feel better.

Exercise may also enhance the activity of special chemicals in the brain called neurotransmitters. Dr. Charles Ransford of Hillsdale College in Michigan has reviewed the data in this area, and although much more study is needed, he speculates that exercise may alter levels of norepinephrine, dopamine, and serotonin, decreasing depression.

Researchers have discovered that during exercise there is an increase in brain emission of alpha waves. These brain waves are associated with a relaxed, meditation-like state, appear 20 minutes into a 30-minute exercise bout, and are still measurable after the exercise is over.

Mental benefits of exercise may also be related to the social support most people get from exercising together. Exercise may also help because it's a distraction or a time-out session from the "real world" of work and responsibility.

Dr. Peter Seraganian from Concordia University in Montreal feels that aerobic fitness shortens the time it takes to recover from stress, and "promotes rapid recovery from an emotional experience.' When fit and unfit individuals are subjected to laboratory-induced stresses such as solving timed arithmetic problems, viewing films of accidents or surgery, or immersing an arm in ice water, aerobically fit persons have a reduced stress response, regardless of the type of stressor.

Other research suggests that exercise decreases muscle electrical tension because of an increase in deep body temperature. There is also some evidence indicating that fit people have an improved quality of sleep, and therefore feel better during the day. And one researcher found blood flow to the brain to increase by as much as 30 percent during moderate bicycling.

Practical implications. One of the amazing facts to come out of research is that the same amount of exercise that helps the heart also helps the brain. The American College of Sports Medicine has established that 30 to 60 minutes of moderate exercise several days a week is essential for health and fitness. Most of the studies mentioned in this article used these same exercise criteria, showing that as the heart is strengthened, so is the brain.

Exercise can act as a buffer, decreasing the strain of stressful events while alleviating anxiety and depression and elevating mood. With exercise, we have a strong weapon to help counter the never-ending onslaught of stress, anxiety, and depression associated with our modern age.

David C. Nieman, Dr.P.H., F.A.C.S.M., is in the Department of Health, Leisure, and Exercise Science at Appalachian State University, Boone, North Carolina.